A further notable feature of the two curves at the lowest photon
numbers are the oscillations after the initial decay of \(\sigma \) .
These are related to the behavior of the photon number density [see
Fig. REF (b)], that exhibits relaxation oscillations analogous
to lasers [1]} or perturbed photon condensates
[2]}. At lower densities, the noise becomes relatively
more important, leading to a more intense creation of new vortex
pairs. Consequently, the vortex number shows oscillations, which
decay together with the photon density oscillations and have the
opposite phase (with some retardation).
